cause rails to correctly place optional path parameter booleans

actionpack/lib/action_dispatch/journey/formatter.rb

@@ -103,7 +103,7 @@ def extract_parameterized_parts(route, options, recall)
           parameterized_parts = recall.merge(options)
 
           keys_to_keep = route.parts.reverse_each.drop_while { |part|
-            !(options.key?(part) || route.scope_options.key?(part)) || (options[part] || recall[part]).nil?
+            !(options.key?(part) || route.scope_options.key?(part)) || (options[part].nil? && recall[part].nil?)
           } | route.required_parts
 
           parameterized_parts.delete_if do |bad_key, _|
@@ -118,7 +118,7 @@ def extract_parameterized_parts(route, options, recall)
             end
           end
 
-          parameterized_parts.keep_if { |_, v| v }
+          parameterized_parts.compact!
           parameterized_parts
         end
 

actionpack/lib/action_dispatch/journey/visitors.rb

@@ -40,7 +40,7 @@ def evaluate(hash)
         @parameters.each do |index|
           param = parts[index]
           value = hash[param.name]
-          return "" unless value
+          return "" if value.nil?
           parts[index] = param.escape value
         end
 

actionpack/test/dispatch/url_generation_test.rb

@@ -16,6 +16,7 @@ def index
 
     Routes.draw do
       get "/foo", to: "my_route_generating#index", as: :foo
+      get "(/optional/:optional_id)/baz", to: "my_route_generating#index", as: :baz
 
       resources :bars
 
@@ -127,6 +128,34 @@ def app
       assert_equal "http://example.com/foo", foo_url(subdomain: "")
     end
 
+    test "keep optional path parameter when given" do
+      assert_equal "http://www.example.com/optional/123/baz", baz_url(optional_id: 123)
+    end
+
+    test "keep optional path parameter when true" do
+      assert_equal "http://www.example.com/optional/true/baz", baz_url(optional_id: true)
+    end
+
+    test "omit optional path parameter when false" do
+      assert_equal "http://www.example.com/optional/false/baz", baz_url(optional_id: false)
+    end
+
+    test "omit optional path parameter when blank" do
+      assert_equal "http://www.example.com/baz", baz_url(optional_id: "")
+    end
+
+    test "keep positional path parameter when true" do
+      assert_equal "http://www.example.com/optional/true/baz", baz_url(true)
+    end
+
+    test "omit positional path parameter when false" do
+      assert_equal "http://www.example.com/optional/false/baz", baz_url(false)
+    end
+
+    test "omit positional path parameter when blank" do
+      assert_equal "http://www.example.com/baz", baz_url("")
+    end
+
     test "generating URLs with trailing slashes" do
       assert_equal "/bars.json", bars_path(
         trailing_slash: true,